Layered thermoplastic-resin-elastomer/rubber product with improved weatherability and pneumatic tire made with the same

ABSTRACT

A thermoplastic resin elastomer/rubber laminate comprising a rubber layer containing 100 parts by weight of a rubber and 0.1-20 parts by weight of an antioxidant preblended thereto and a thermoplastic resin elastomer composition layer, obtained by laminating at least two layers of the rubber layer and the thermoplastic resin elastomer composition layer followed by heating and pressing, whereby the antioxidant migrates from the rubber layer to the thermoplastic resin elastomer composition layer to improve the weathering resistance as well as a pneumatic tire using the same as an inner liner.

TECHNICAL FIELD

The present invention relates to a laminate of a thermoplastic resinelastomer composition layer and a rubber layer, more specifically,relates to a thermoplastic elastomer/rubber laminate having an improvedweathering resistance useful as, for example, an inner liner of apneumatic tire and also relates to a pneumatic tire using the same.

BACKGROUND ART

A thermoplastic elastomer/rubber layer having a layer using acomposition of a thermoplastic resin and an elastomer (i.e., athermoplastic elastomer composition layer) on the surface of a rubberlayer is, for example, described in Japanese Patent No. 3217239, etc.and has characteristics such as flexibility, low temperature durability.However, an elastomer/rubber laminate having a thermoplasticelastomer/rubber composition on the surface thereof, when used in astate exposed to the outside, is subjected to UV light, heat, oxygen,ozone, etc. and the thermoplastic resin elastomer composition layer isaged, whereby cracks are formed and other problems in the weatheringresistance occur. Therefore, when an antioxidant is compounded inadvance to the composition so as to improve the aging resistance of thethermoplastic resin elastomer composition, while mixing thethermoplastic resin and elastomer, the antioxidant acts as anaccelerator. Particularly, when using rubber as an elastomer, scorchingof the rubber occurs, and therefore, there was the problem that acomposition having the desired physical properties can not be obtained.

DISCLOSURE OF THE INVENTION

Accordingly, the objects of the present invention are to eliminate theabove problems in the prior art and to provide a thermoplastic resinelastomer/rubber laminate having an improved weathering resistance.

In accordance with the present invention, there are provided athermoplastic elastomer/rubber laminate comprising a rubber layercontaining 100 parts by weight of a rubber and 0.1-20 parts by weight ofan antioxidant preblended thereto and a thermoplastic resin elastomercomposition layer, obtained by laminating at least two layers of therubber layer and the thermoplastic resin elastomer composition layer,followed by press vulcanizing the laminate, whereby the antioxidantmigrates from the rubber layer to the thermoplastic resin elastomercomposition layer to improve the weathering resistance as well as apneumatic tire using, as an inner liner, the same.

In accordance with the present invention, when producing a laminate of athermoplastic resin elastomer composition layer and a rubber layer, anantioxidant, preferably an amine-based antioxidant, is compounded intothe rubber layer in advance, a composition layer comprising athermoplastic resin and an elastomer is laminated thereon, followed by,for example, press-vulcanizing the laminate, whereby the antioxidantmigrates from the rubber layer to the thermoplastic resin elastomercomposition layer, and therefore, the weathering resistance of thethermoplastic resin elastomer composition layer is improved. By, forexample, press-vulcanizing the unvulcanized rubber containing theantioxidant compounded therein, in such a manner, the antioxidantmigrates from the rubber layer to the thermoplastic resin elastomercomposition layer and as a result, a laminate of the thermoplastic resinelastomer composition containing the migrated antioxidant and thevulcanized rubber is obtained. By arranging this laminate such that thethermoplastic elastomer composition layer contacts the outside air, itis possible to remarkably suppress the aging, the generation of cracks,etc. of the laminate due to the influence by ultraviolet light, heat,oxygen, ozone, etc.

BEST MODE FOR CARRING OUT THE INVENTION

The rubber layer of the laminate according to the present invention,includes any diene-based rubber capable of using for a tire such as, forexample, natural rubbers (NR), polyisoprene rubbers (IR), variousstyrene-butadiene copolymer rubbers (SBR), various polybutadiene rubbers(BR), acrylonitrile-butadiene copolymer rubbers (NBR), chloroprenerubbers (CR), etc. These rubbers may be used alone or in any blendsthereof. Further, a blend containing non-diene-based rubbers such asbutyl rubbers (IIR), ethylene-propylene-diene terpolymer rubbers (EPDM),etc. may also be used in small amounts.

The thermoplastic resin elastomer layer of the laminate according to thepresent invention is comprised of a thermoplastic resin having anelastomer blended thereinto. As such a thermoplastic resin,polyamide-based resins (e.g., nylon 6 (N6), nylon 66 (N66), nylon 11(N11), nylon 12 (N12), nylon 610 (N610), nylon 612 (N612), etc.),polyester-based resins (e.g., polybutylene terephthalate (PBT),polyethylene terephthalate (PET), polyethylene isophthalate (PEI),etc.), polynitrile-based resins (e.g., polyacrylonitrile (PAN),polymethacrylonitrile, etc.), polymethacrylate-based resins (e.g.,polymethyl methacrylate (PMMA), polyethyl methacrylate, etc.),polyvinyl-based resins (e.g., vinyl acetate, polyvinyl alcohol (PVA),polyvinylidene chloride (PDVC), polyvinyl chloride (PVC), etc.),cellulose-based resins (e.g., cellulose acetate and cellulose acetatebutyrate), fluorine-based resins (e.g., polyvinylidene fluoride (PVDF),polyvinyl fluoride (PVF), etc.), imide-based resins (e.g., an aromaticpolyimide (PI)), etc. may be mentioned.

As the elastomer blended with the thermoplastic resin according to thepresent invention, for example, a diene-based rubbers and thehydrogenates thereof (e.g., NR, IR, SBR, BR, NBR, etc.), olefin-basedrubbers (e.g., ethylene propylene rubbers (EPDM, EPM), IIR, etc.), acrylrubbers (ACM), halogen-containing rubbers (e.g., Br-IIR, Cl-IIR,bromides of isobutylene paramethyl styrene copolymers (Br-IPMS, etc.),silicone rubbers (e.g., methylvinyl silicone rubber, dimethyl siliconerubber, etc.), sulfur-containing rubbers (e.g., polysulfide rubber),fluorine rubbers (e.g., a vinylidene fluoride-based rubber, andfluorine-containing vinyl ether-based rubber), thermoplastic elastomers(e.g., a styrene-based elastomer, olefin-based elastomer, ester-basedelastomer, urethane-based elastomer and polyamide-based elastomer), etc.may be mentioned. These may be used alone or in any mixtures thereof twotypes.

The above-mentioned elastomer components may also be dynamicallyvulcanized when mixing with the thermoplastic resin. Here, the “dynamicvulcanization” means the method of finely dispersing the elastomercomponent in the thermoplastic resin and simultaneously cross-linkingand immobilizing the elastomer component. The types of a vulcanizingagent and a vulcanizing aid and vulcanization conditions (temperatureand time), etc. in the case of dynamic vulcanization may be suitablydetermined depending upon the composition of the elastomer componentadded and is not particularly limited. As the vulcanization agent, ageneral rubber vulcanizing agent (or cross-linking agent) may be used.Specifically, as a sulfur-based vulcanizing agent, sulfur powder,precipitated sulfur, etc. may be used in an amount of, for example,about 0.5 to 4 phr (parts by weight based upon 100 parts by weight ofthe rubber component (polymer)).

Further, as the organic peroxide-based vulcanization agent,benzoylperoxide, t-butylhydroperoxide, 2,4-bichlorobenzoylperoxide, etc.may be mentioned and, as the thiourea-based vulcanizing accelerator,ethylene thiourea, diethyl thiourea, etc. may be mentioned.

Further, as the vulcanizing aid, conventional rubber aids may be usedtogether. For example, zinc white (approximately 5 phr (i.e., parts byweight based upon 100 parts by weight of the elastomer), stearic acid,oleic acid and their Zn salts (approximately 2 to 4 phr), etc. may beused. The production method of the thermoplastic elastomer compositioncomprises melt mixing, in advance, the thermoplastic resin component andthe elastomer component (in the case of rubber, unvulcanized) by atwin-screw extruder etc. and dispersing the same in the thermoplasticresin to thereby form the continuous phase (or matrix phase), in whichthe elastomer component is dispersed, as the dispersed phase (ordomain). When vulcanizing the elastomer component, it is also possibleto add the vulcanization agent, while mixing, to dynamically vulcanizethe elastomer component. Further, the various compounding agents for thethermoplastic resin or elastomer component (except for the vulcanizationagent) may be added during the mixing, but preferably are premixedbefore the mixing. The mixing machine used for mixing the thermoplasticresin and elastomer components is not particularly limited, but a screwextruder, kneader, Banbury mixer, twin-screw extruder, etc. may be used.As the conditions for the melt mixing, the temperature may be anytemperature or more where the thermoplastic resin melts. Further, theshear rate, when mixing, is preferably 1000 to 7500 sec⁻¹. The totalmixing time is 30 seconds to 10 minutes. Further, when adding avulcanization agent, the vulcanization time after adding is preferably15 seconds to 5 minutes. The thermoplastic elastomer compositionprepared by the above method is extrusion molding or calendar molding toa sheet-like film. The film formation method may be a conventionalmethod of forming a film from a thermoplastic resin or thermoplasticelastomer.

The film thus obtained has a structure such that a matrix of athermoplastic resin (A) into which an an elastomer component (B) isdispersed as a dispersed phase (i.e., domain). By adopting this state ofa dispersed structure, thermoplastic processing becomes possible and thefilm can be provided with a sufficient flexibility. Further, it ispossible to impart sufficient rigidity due to the effect of the resinlayer as the continuous phase. Further, regardless of the amount of theelastomer component, at the time of molding, it is possible to obtain amoldability of the same extent as a thermoplastic resin, and therefore afilm can be formed by a conventional resin molding machine, that is, byextrusion or calendar molding.

The specific ratio of the thermoplastic resin (A) and the elastomercomponent (B), when blending the thermoplastic resin and the elastomer,is not particularly limited and may be suitably determined by thebalance of the film thickness, anti-air permiability and flexibility,but the preferable range is a weight ratio (A)/(B) of 10/90 to 90/10,more preferably 15/85 to 90/10.

As the antioxidant blended, in advance, into the rubber layer side,according to the present invention, for example, amine-basedantioxidants such as naphthylamine-based antioxidants such asphenyl-2-naphthylamine, phenyl-l-naphthylamine, diphenylamine-basedantioxidants such as 4,4′-α,α-dimethylbenzyl) diphenylamine,p-(P-toluene-sulfonylamide)-diphenylamine, p-phenylenediamine-basedantioxidants such as N,N′-diphenyl-p-phenylenediamine,N-isopropyl-N′-phenyl-p-phenylenediamine are preferably used, but theirderivatives or mixtures may also be used.

According to the present invention, the amount of the antioxidantcompounded into the rubber layer is 0.1 to 20 parts by weight,preferably 0.1 to 10 parts by weight, based upon 100 parts by weight ofthe rubber. If the compounded amount is too small, the desiredweathering resistance cannot be obtained, whereas if too large, bloomingunpreferably occurs.

The laminate of the thermoplastic resin elastomer composition layer andthe rubber layer according to the present invention may be made by ageneral method as used in the past. For example, it may be made bycoating, lamination, coextrusion, etc. Further, the method of bondingthe thermoplastic resin elastomer composition layer and the rubber layeris not particularly limited, but, for example an adhesive, cement,direct bonding any other suitable method may be used.

The layer containing the thermoplastic resin elastomer composition andthe rubber layer, in which 0.1 to 20 parts by weight based upon 100parts by weight of rubber, of an antioxidant is preblended, do notnecessarily have to be in direct contact. So long as the antioxidant ismigrated to the thermoplastic resin elastomer composition by heating andpressing, it is possible to laminate the layers through a layer composedof another layer, which is sandwiched between the two layers.

The thermoplastic resin elastomer composition or the rubber compositionaccording to the present invention may include, in addition to theessential components, any additives conventionally compounded into thethermoplastic elastomer compositions or the rubber compositions. Forexample, it is possible to compound therein carbon black, silica, orother fillers, a vulcanization or cross-linking agent, a vulcanizationor cross-linking accelerator, various types of oil, an antioxidant, aplasticizer, or other various types of additives conventionally used fortire or other general rubber use. The additives may be used for mixingand vulcanizing by a conventional method to obtain a composition andused for vulcanization or cross-linking. The compounded amounts of theseadditives may be the conventional compounding amounts so long as theobject of the present invention is not impaired.

EXAMPLES

Examples will now be used to further explain the present invention, butthe scope of the present invention is by no means limited to theseExamples.

Examples 1 to 11 and Comparative Example 1

Preparation of Sample of Sheet-Like Thermoplastic Resin ElastomerComposition

0.3 part by weight of ZnO, 1.2 parts by weight of zinc stearate and 0.6part by weight of stearic acid were mixed to 100 parts by weight of apartially bromided polyisobutylene-p-methylstyrene copolymer (BIMS:Exxpro 89-4) by an internal Banbury mixer at an initial temperature of40° C. for 5 minutes to prepare a rubber master batch. Thus, this rubbermaster batch was pelletized by a rubber pelletizer. 50 parts by weightof the rubber pellets thus obtained, 13 parts by weight of a nylon 6,66copolymer (Toray Amylan CM6041) and 25 parts by weight of nylon 11(Atofina Rilsan BMNO) were dynamically vulcanized by a twin-screwextruder at a temperature of 220° C. for 5 minutes, followed bypelletized. The pellets thus obtained were extruded by a T-die to form a0.1 mm thick film.

Preparation of Rubber Sheet Sample

The ingredients other than the vulcanization accelerator and the sulfurin the formulation shown in Table I were mixed by a 1-liter internalmixer for 5 minutes and discharged when reaching 165±5° C. to obtain amaster batch. The vulcanizing accelerator and the sulfur were mixed intothe master batch by an open roll to obtain a sheet-like rubbercomposition.

Test Methods for Evaluation of Physical Properties

The sheet-like thermoplastic resin elastomer composition prepared abovewas brush coated with a rubber-based cement of the formulation shown inTable II, dried, laminated with a sheet-like rubber composition (i.e., 2mm sheet) prepared above and then vulcanized at 190° C. for 10 minutes.The laminate of the thermoplastic resin elastomer composition and therubber obtained (i.e., for carcass use) was punched to obtain a samplefor a constant strain fatigue test by a JIS No. 2 Dumbbell.

Thereafter, a sample deterioration test was carried out as follows by anopen frame carbon arc lamp.

The procedure according to the SA method of JIS K6266 was followed for adeterioration test on the laminate sample of the thermoplastic resinelastomer composition and the rubber laminate. The sample was set insuch a manner that the thermoplastic resin elastomer composition sidewas faced to the light source. The test temperature was 63° C., thelight was continuously irradiated and water was sprayed on the surfaceof the test piece at a cycle of 18 minutes every 102 minutes. Thedeterioration times were 48 hours, 96 hours, and 168 hours. Samplestaken out at these times were evaluated for durability performance bythe constant strain fatigue test explained below. The results are shownin Table I.

Constant Strain Fatigue Test Method

Each sample after the deterioration test was subjected to a constantstrain fatigue test, in which 40% repeated elongation strain was appliedat a 6.7 Hz cycle at 20° C. and evaluated for durability performance.The stage when the surface of the thermoplastic resin elastomer crackedwas deemed the end of the evaluation. The evaluation was ended with 10million repeated fatigue cycles.

TABLE I Comp. Example Name of material Manufacturer and grade Ex. 1 1 23 4 5 6 7 8 9 10 11 Formulation (parts by weight) Natural rubber RSS #380 80 80 80 80 80 80 80 80 80 80 80 SBR 1502 Nippon Zeon, Nipol 1502 2020 20 20 20 20 20 20 20 20 20 20 FEF carbon black Chubu Carbon, HTC #10050 50 50 50 50 50 50 50 50 50 50 50 Stearic acid NOF Corp., BeadsStearic 2 2 2 2 2 2 2 2 2 2 2 2 Acid NY Zinc oxide Seido Chemical, Zinc3 3 3 3 3 3 3 3 3 3 3 3 White #3 Sulfur Karuizawa Refinery, sulfur 3 3 33 3 3 3 3 3 3 3 3 powder Vulcanizing accelerator NS Ouchi ShinkoChemical 1 1 1 1 1 1 1 1 1 1 1 1 Industrial, Noccelar NS-P Aromatic oilShowa Shell Oil, Desolex #3 2 2 2 2 2 2 2 2 2 2 2 2 2,2,4-trimethyl-1,2-Ouchi Shinko Chemical — 2 — — — — — — — — — — dihydroquinoline polymerIndustrial, Nocrac 224 6-ethoxy-1,2-dihydro-2,2,4- Ouchi Shinko Chemical— — 2 — — — — — — — — — trimethylquinoline Industrial, Nocrac AWDiphenylamine and acetone Ouchi Shinko Chemical — — — 2 — — — — — — — —reaction product Industrial, Nocrac B Phenyl-1-naphthylamine OuchiShinko Chemical — — — — 2 — — — — — — — Industrial, Nocrac PA Alkylateddiphenylamine Ouchi Shinko Chemical — — — — — 2 — — — — — — Industrial,Nocrac ODA N,N′-di-naphthyl-p- Ouchi Shinko Chemical — — — — — — 2 — — —— — phenylenediamine Industrial, Nocrac White N-phenyl-N′-isopropyl-p-Ouchi Shinko Chemical — — — — — — — 2 — — — — phenyldiamine Industrial,Nocrac 810MA p-(p-toluenesulfonyl- Ouchi Shinko Chemical — — — — — — — —2 — — — amide)diphenylamine Industrial, Nocrac TD Mixture ofp-styrenated Seiko Chemical, Nonflex LAS — — — — — — — — — 2 — —diphenylamine and p,p′- distyrenated diphenylamineN-phenyl-N′-(1,3-dimethyl- Ouchi Shinko Chemical — — — — — — — — — — 2 —butyl)-p-phenyldiamine Industrial, Nocrac 6C N-phenyl-N′-(3- OuchiShinko Chemical — — — — — — — — — — — 2 methacryloyloxy-2- Industrial,Nocrac G-1 hydroxypropyl)-p- phenyldiamine Evaluated physical propertiesOpen frame carbon arc Deterioration time (48 hours) 4.0 1000 1000 10001000 1000 1000 1000 1000 1000 1000 1000 lamp deterioration time andDeterioration time (96 hours) 0.1 480 800 720 510 520 315 1000 300 10001000 1000 constant strain fatigue test Deterioration time (168 hours)Eval. 255 635 440 350 310 110 1000 80 900 1000 950 stopped

TABLE II Rubber-Based Cement Compounded amount (parts by Name ofmaterial Manufacturer and grade weight) Natural rubber RSS #3 80 SBR1502Nippon Zeon Nipol 1502 20 FEF carbon black Chubu Carbon HTC #100 50Stearic acid NOF Corp. Beads Stearic 2 Acid NY Zinc oxide Seido ChemicalZinc 3 White #3 Sulfur Karuizawa Refinery sulfur 3 powder Vulcanizingaccelerator Ouchi Shinko Chemical 1 NS Industrial Noccelar NS-P Aromaticoil Showa Shell Oil Desolex #3 2 Hexamethoxymethylated Mitsui CytecCYREZ-964RPC 5 melamine Resorcinol-formaldehyde Indspec ChemicalPenacolite 10 resin Resin B-18-S Phenol formaldehyde Hitachi ChemicalHitanol 1502Z 1 resin Toluene Reagent grade toluene 1000

INDUSTRIAL APPLICABILITY

As mentioned above, according to the present invention, by laminatingcomposition a thermoplastic resin and elastomer having desired physicalproperties and an unvulcanized rubber composition, to which anantioxidant is preblended, it is possible for the antioxidant to migratefrom the adjacent rubber layer to the thermoplastic resin elastomerlayer, whereby the weathering resistance is improved, and therefore,this is extremely useful as, for example, the inner liner of a pneumatictire.

1. A thermoplastic elastomer/rubber laminate comprising at least onerubber layer containing 100 parts by weight of a rubber and 0.1-20 partsby weight of an antioxidant preblended thereto and at least onethermoplastic elastomer composition layer, obtained by laminating atleast two layers of the at least one rubber layer and the at least onethermoplastic elastomer composition layer, followed by heating andpressing, whereby the antioxidant migrates from the rubber layer to thethermoplastic elastomer composition layer to improve the weatheringresistance, said antioxidant being selected from the group consisting ofN-phenyl-N′-(1,3-dimethyl-butyl)-p-phenylenediamine and N-phenylN′-isopropyl-p-phenylenediamine and said thermoplastic elastomercomposition comprising (A) at least one resin selected from the groupconsisting of polyamide-based resins, polyester-based resins,polynitrile-based resins, polymethacrylate resins, vinyl acetate-basedresins, polyvinyl alcohol, polyvinylidene chloride, polyvinyl chloride,fluorine-based resins and imide-based resins and (B) at least oneelastomer selected from the group consisting of diene-based rubbers andthe hydrogenates thereof, acryl rubbers, halogen-containing rubbers,silicone rubbers, sulfur-containing rubbers, fluorine rubbers andthermoplastic elastomers.
 2. A laminate as claimed in claim 1, wherein aratio (A)/(B) (by weight ratio) of an thermoplastic resin (A) and anelastomer (B) in the thermoplastic elastomer composition is 10/90 to90/10.
 3. A laminate as claimed in claim 2, wherein the thermoplasticresin (A) is at least one polyamide-based resin.
 4. A laminate asclaimed in claim 2, wherein the elastomer (B) is at least one rubberselected from the group consisting of diene-based rubbers and theirhydrogenates.
 5. A laminate as claimed in claim 1, wherein the rubberforming the rubber layer is at least one rubber selected from the groupconsisting of natural rubbers, styrene-butadiene copolymer rubbers,polybutadiene rubbers, chloroprene rubbers, butyl rubbers andethylene-propylene-diene terpolymer rubbers.
 6. A pneumatic tire using,as an inner liner, a laminate according to claim
 1. 7. A laminate asclaimed in claim 1, wherein the amount of the antioxidant is 2-20 partsby weight, based upon 100 parts by weight of the rubber.
 8. A laminateas claimed in claim 1, wherein the antioxidant isN-phenyl-N′-(1,3-dimethyl-butyl)-p-phenylenediamine.